Phased arrays are deployed in a number of electronic systems where high beam directivity and/or electronic scanning of the beam is desired. Applications range from radar systems to smart antennas in wireless communications. It has been known for quite some time that errors (random and/or correlated fluctuations) present in the excitation coefficients of a phased array can degrade its performance. Undesirable effects resulting from errors in the magnitude and phase of the array coefficients can include decrease in directivity, increase in sidelobes, and steering the beam in a wrong direction. The degradation can be particularly severe for high-performance arrays designed to produce low sidelobes or narrow beam-width. For example, in satellite communications, where high directivity and low sidelobes are often required, degradation of the radiation pattern will result in requiring higher transmit power or cause interference to neighboring satellites, both of which are undesirable. The sources of these errors can be many ranging from those induced by environmental changes to those caused by mistuned or failed amplifiers and phase shifters.